An ejector cycle of a vapor-compression refrigerant cycle in an air-conditioner for a vehicle is performed by an ejector. In the ejector cycle, the ejector decompresses and expands high-pressure refrigerant so that suction pressure of a compressor is increased in accordance with converting expansion energy to pressure energy and that refrigerant of a low-pressure side circulates by a pumping operation of the ejector.
Here, the pumping operation of the ejector provides a momentum transportation type pumping, which performs to suck fluid by jetting the refrigerant at high speed, as described in Japan Industrial Standard Z 8126 No. 2.1.2.3. This pumping performance of the ejector changes in accordance with an opening degree of a throttle of a nozzle in the ejector. When the opening degree of the throttle is fixed, the pumping performance of the ejector is limited. In some cases, the ejector may not send the refrigerant to the evaporator sufficiently, so that the cooling performance of the air-conditioner becomes short.
Moreover, when the cooling performance of the air-conditioner reduces, a dehumidifying performance of the air-conditioner also reduces, so that a windshield of the vehicle may be fogged.